A battery is generally used in mobile devices such as a mobile phone and a personal digital assistant (PDA). As a battery most commonly used in the mobile devices, a lithium ion battery is heated when overcharge or overcurrent occurs, and even has the risk of explosion as well as performance degradation if heating is continued and thus temperature thereof is increased. Accordingly, a typical battery may include a protection circuit device for detecting overcharge, overdischarge, and overcurrent and blocking operation of the battery. This conventional protection circuit device is generally produced by soldering a protection integrated circuit (IC), a field effect transistor (FET), resistors, capacitors, etc. on a printed circuit board (PCB). However, the conventional protection circuit device may not easily achieve a small size because the PCB occupies an excessively large space. Furthermore, after the protection circuit device is mounted on a battery core pack, a process for electrically connecting the same to external connection terminals or internal connection terminals through additional wires, wire bonding, or exposed terminals of the PCB is complicated and not easy.